1. Field of the Invention
The present invention relates to systems and methods for analyzing signals, and more particularly to a system and method for analyzing jitter of signals.
2. General Background
Jitter in serial data communication is a difference of data transition times relative to ideal bit clock active transition times. Jitter represents a deviation, typically in picoseconds, from the ideal. As data transfer rates increase within semiconductor devices and other high speed applications increase, the jitter component may become more significant. For example, in video graphics chips, jitter can cause a flicker or jumping of the video image. Also, in serial data communication systems jitter will cause errors. In order to understand the effects that jitter may have on semiconductor devices and data communication systems, measurements of jitter and other aspects of timing are critical during the prototyping stages and production tests.
Jitter has four major components which include inter-symbol interference, cycle jitter, periodic jitter, and random jitter. The inter-symbol interference is caused by a data path propagation delay that is a function of past data history and occurs in all finite bandwidth data paths. The cycle jitter is caused by different propagation delays for positive and negative data transitions. The periodic jitter is caused by one or more sine waves and its/their harmonics. The random jitter is assumed to be Gaussian and has a power spectral density that is a function of frequency. The inter-symbol interference, cycle jitter and periodic jitter are all bounded, and they may be described as a peak or peaks to peaks value in bit period, unit interval (UI) or seconds. In contrast, the random jitter is unbounded, and it may be described by a standard deviation in UIs or seconds.
As semiconductor devices and data communication systems development, analyzing the jitter components is valuable to the product designers and testers. For example, measuring the periodic jitter helps determine whether there is cross-talk on a circuit. Analyzing the inter-symbol interference and the cycle jitter permits the cause of the bit error rate to be determined.
However, present available measurement instruments do not separate the jitter components. For example, oscilloscopes show jitter as an overall distribution without a separation of the random jitter and the periodic jitter. Although spectrum analyzers may measure jitter, they typically cannot be used on data streams. Further, when a spectrum analyzer measures a jitter value it does not separate the periodic jitter and the random jitter. Moreover, the present available spectrum analyzers are typically used to analyzing measurement signals, and are not used to analyzing simulation signals in a type of document. Also, formats of the measurement signals and the simulation signals are not compatible.
What is needed, therefore, is an extensive and compatible computer system for analyzing jitter of various signals, which can be compatible for the measurement signals and the simulation signals, and which can output various comparable analysis waves and analysis results.
Similarly, what is also needed is an extensive and compatible method for analyzing jitter of various signals, which can be compatible for the measurement signals and the simulation signals, and which can output various comparable analysis waves and analysis results.